Select the correct statement(s) with respect to the `p pi-dpi` dative bond.

Options

A. In `(Ph_3Si)_2O`, the Si-O-Si group is nearly linear
B. Silanols such as `(CH_3)_3` SiOH are stronger protonic acids then their carbon analogs
C. Trisilysl phosphine `(H_3Si)_3` P is planar
D. `CIO_4^-` does not polymerise at all

Explanation

To solve the question regarding the correct statements about the `p pi-d pi` dative bond, we will analyze each statement provided in the question step by step.

### Step-by-Step Solution:

1. **Statement 1: In Ph3Si2O, the Si-O-Si group is nearly linear.**
- **Analysis**: The presence of bulky phenyl groups creates steric hindrance, which favors a linear arrangement for the Si-O-Si group. Additionally, the p-pi-d-pi bonding contributes to this linearity.
- **Conclusion**: This statement is **correct**.

2. **Statement 2: Silanols such as CH3-3SiOH are stronger protonic acids than their carbon analogs.**
- **Analysis**: Silanols can donate protons (H+) easily due to the stability of the resulting anion (CH3)3SiO-. This stability arises from the p-pi-d-pi bonding between the p orbital of oxygen and the d orbital of silicon. Carbon analogs lack d orbitals, which makes them less capable of stabilizing the anion formed after proton donation.
- **Conclusion**: This statement is **correct**.

3. **Statement 3: Trisilylphosphine is planar.**
- **Analysis**: Trisilylphosphine does not exhibit planarity because the d-pi-pi bonding is not effective due to the larger size of phosphorus. The larger atomic size prevents effective overlap necessary for planar structures.
- **Conclusion**: This statement is **incorrect**.

4. **Statement 4: ClO4- does not polymerize at all.**
- **Analysis**: The ClO4- ion is stable and exists as a monomer due to the effective d-pi-pi bonding, which is facilitated by the small size of chlorine. This prevents polymerization.
- **Conclusion**: This statement is **correct**.

### Final Conclusion:
The correct statements regarding the `p pi-d pi` dative bond are:
- Statement 1: Correct
- Statement 2: Correct
- Statement 3: Incorrect
- Statement 4: Correct

Thus, the correct statements are **1, 2, and 4**.